title: Visual analog scale (VAS) for assessment of acute mountain sickness (AMS) on Aconcagua.
abstract: OBJECTIVE
  The Lake Louise AMS Self-Report Score (LLSelf) is a commonly used, validated assessment of acute mountain sickness (AMS). We compared LLSelf and visual analog scales (VAS) to quantify AMS on Aconcagua (6962 m).
  
  
  METHODS
  Prospective observational cohort study at Plaza de Mulas base camp (4365 m), Aconcagua Provincial Park, Argentina. Volunteers climbing in January 2009 were enrolled at base camp and ascended at their own pace. They completed the LLSelf, an overall VAS [VAS(o)], and 5 individual VAS [VAS(i)] corresponding to the items of the LLSelf when symptoms were maximal. Composite VAS [VAS(c)] was calculated as the sum of the 5 VAS(i).
  
  
  RESULTS
  A total of 127 volunteers consented to the study. Response rate was 52.0%. AMS occurred in 77.3% of volunteers, while 48.5% developed severe AMS. Median (interquartile range, IQR) LLSelf was 4 (3-7). Median (IQR) VAS(o) was 36 mm (23-59). VAS(o) was linear and correlated with LLSelf: slope = 6.7 (95% CI: 4.4-9.0), intercept = 3.0 (95% CI: -10.0-16.1), ρ = 0.71, τ = 0.55, R(2) = 0.45, p < 0.001. Median (IQR) VAS(c) was 29 (13-44). VAS(c) was also linear and correlated with LLSelf: slope = 5.9 (95% CI: 4.9-6.9), intercept = -0.6 (95% CI: -6.3-5.1), ρ = 0.83, τ = 0.68, R(2) = 0.73, p < 0.001. The relationship between the 5 VAS(i) and LLSelf(i) was less significant and less linear than that between VAS(o), VAS(c), and LLSelf.
  
  
  CONCLUSIONS
  While both VAS(o) and VAS(c) for assessment of AMS appear to be linear with respect to LLSelf, the amount of scatter within the VAS is considerable. The LLSelf remains the gold standard for the diagnosis of AMS.
authors.affiliation: Department of Emergency Medicine, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA. vanroo@gmail.com
authors.forename: Jon D
authors.initials: JD
authors.lastname: Van Roo
authors.forename: Matthew P
authors.initials: MP
authors.lastname: Lazio
authors.forename: Carlos
authors.initials: C
authors.lastname: Pesce
authors.forename: Sanjeev
authors.initials: S
authors.lastname: Malik
authors.forename: D Mark
authors.initials: DM
authors.lastname: Courtney
mesh_terms: D000208:Acute Disease; D000328:Adult; D000532:Altitude Sickness / Q000145:classification / Q000175:diagnosis*; D001118:Argentina; D015331:Cohort Studies; D005260:Female; D006801:Humans; D008297:Male; D009051:Mountaineering; D010147:Pain Measurement; D011446:Prospective Studies; D015203:Reproducibility of Results; D012647:Self-Assessment; D012720:Severity of Illness Index